There is a need regarding the backrest of seats such as automobile and office seats and armchairs to adjust the lordotic region in controlled manner in hardness and contour in order to effectively support the anatomically proper curvature of the spinal column also during prolonged sitting. Where called for the position also shall be height-adjustable to allow contour or hardness adjustment in taller people whose lordotic region is somewhat higher, whereas a zone situated farther below shall be selectable as regards shorter people.
The German patent 199 24 591 describes a system implementing padding enhancement for a seat's backrest which comprises a number of leaf spring elements in the lordotic region that run transversely to the backrest and act as padding support. The longitudinal support may be deformed in a direction perpendicular to it. An adjusting device allows displacing the spring element in the zone of the longitudinal support whereby the shape of the padding support will change. Said known document also discloses using at least one resiliently supported element that may be moved to-and-fro the seat surface and/or the backrest surface. A telescoping adjustment system comprises at least two mutually nesting cylindrical tubes of which the threaded segments cooperate in such manner that upon rotation of the outer tube, the inner tube shall be adjusted in the direction of the common axis, the outer tube being rotatable but axially fixed in position, and said adjustment system is used to drive the resiliently supported element. The adjustment system's outer tube is linked to a rotational drive element.
The German patent 23 39 069 discloses a vehicle seat which also allows supporting the backrest vertebral zone by making the backrest bulge in the lordotic region. The bulging zone may be made to more or less pre-bulge at appropriate time intervals. The purpose is to attain alternating enlargement and reduction in size of the intervertebral spaces in order to improve the metabolism of the intervertebral disks and of the tissue surrounding latter.